3
Correcting Magnitudes for Distance
•To correct intensity or flux for distance, use Inverse Square Law
•
•
•
•Up to now we have used “apparent magnitudes”  mv
•Define absolute magnitude Mv as magnitude star would have
 if it were at a distance of 10 pc.
•
•
•
•
•
•
•
•This gives us a way to correct Magnitude for distance, or find distance if we know absolute magnitude
•
•Note:  the book writes mv and Mv:  The “V” stands for “Visual”
–Later we’ll consider magnitudes in other colors like “B=Blue” “U=Ultraviolet”
•
•
•